In TDI engines, a fuel injector sprays atomized fuel directly into the main combustion chamber of each cylinder. This is different from engines that utilize a pre-combustion chamber, which has been prevalent in older indirect injection engines. TDI engines also use forced induction by way of a turbocharger in order to increase the amount of air entering the engine cylinders. TDI engines also typically use an intercooler to increase the amount of fuel that can be injected and combusted per engine cycle. These features allow TDI engines to provide improved engine efficiency, and therefore greater power output, while also decreasing emissions compared to more conventional engine designs.
These benefits, however, come with some challenges. Deposit formation in TDI engines, particularly piston deposit formation, is generally harder to control than it is in other engine designs, likely due to the same features that increase overall efficiency. This may be due to the fact that TDI engines have a low surface area because they have relatively low displacement and are quite compact compared to other engine designs. Regardless of the primary cause, this deposit formation can impact engine performance and result in reduced performance and increased maintenance costs. Thus, there is an ongoing need for additives, and lubricating compositions containing the same, specifically designed for TDI engines, that provide improved deposit control, particularly piston deposit control.